Swift observations of the X-ray and UV evolution of V2491 Cyg (Nova Cyg 2008 No. 2)

TL;DR

This paper presents detailed Swift observations of V2491 Cyg, tracking its X-ray and UV evolution through various phases of the nova outburst, revealing insights into its magnetic nature and recurrence potential.

Contribution

It provides the first high-density, multi-phase X-ray and UV observational data of V2491 Cyg, analyzing its spectral evolution and magnetic characteristics.

Findings

X-ray emission observed one day after discovery.

UV and X-ray light-curves show different evolution paths.

No periodic signal suggests the white dwarf is likely non-magnetic.

Abstract

We present extensive, high-density Swift observations of V2491 Cyg (Nova Cyg 2008 No. 2). Observing the X-ray emission from only one day after the nova discovery, the source is followed through the initial brightening, the Super-Soft Source phase and back to the pre-outburst flux level. The evolution of the spectrum throughout the outburst is demonstrated. The UV and X-ray light-curves follow very different paths, although changes occur in them around the same times, indicating a link between the bands. Flickering in the late-time X-ray data indicates the resumption of accretion. We show that if the white dwarf is magnetic, it would be among the most magnetic known; the lack of a periodic signal in our later data argues against a magnetic white dwarf, however. We also discuss the possibility that V2491 Cyg is a recurrent nova, providing recurrence timescale estimates.